This post explores the weeds of Cascading Style Sheets (CSS), the language that creates the design for web pages. CSS 'specificify' rules to the method web browsers use to select which CSS declaration to apply to a particular part of a web page. For example, if you said the default text style for your whole page is 'Arial' and the default text style for this paragraph is 'Times New Roman', your browser needs to make a choice (and will choose the latter, according to CSS specificity). There's also a link to a lovely diagram, CSS Specificity with fish.